Huge hype surrounds the launch of each new games console - the Sony Playstation 2 is just the latest. But should parents be worried by their children's passion for virtual play?

Foremost among the criticisms levelled at video games is that they are addictive.

The charge goes that they can lead to compulsive behaviour, loss of interest in other activities, association mainly with other addicts, and unusual symptoms when addicts are denied their favourite pastime - such as the shakes. Sound familiar?

Are players becoming too attached to games consoles?

A decade ago research showed that video game junkies were highly intelligent, motivated and achievement-oriented individuals. They did well at school and work.

But could the more sophisticated games of the 21st Century be so all-consuming as to interfere with that kind of achievement?

Dr Mark Griffiths of Nottingham Trent University, an expert on video game addiction, thinks it could just happen.

"The video games of the 21st Century may in some ways be more psychologically rewarding than the 1980s games in that they require more complex skills, improved dexterity, and feature socially relevant topics and better graphics."

Game addicts

If these games offer greater "psychological rewards", players might be more at risk of developing an addiction, he said.

Children are drawn to video games at about the age of seven. For most, the games remain a harmless activity, but a small minority could be termed "addicts".

Game playing can be a social activity

A recent study of children in their early teens found that almost a third played video games daily, and that - more worryingly - 7% played for at least 30 hours a week.

Dr Griffiths is concerned by that figure.

He said: "What are the long-term effects of any activity that takes up 30 hours of leisure time a week on the educational, health and social development of children and adolescents?"

Such dependency could feed other delinquent behaviour such as stealing money to buy new games, truancy, failing to do homework, or simply extreme annoyance when unable to play.

So how are concerned parents to decide when school plus video games equals overload?

Dr Griffiths has a ready reckoner:

Does your child:

play almost every day?

often play for long periods (over 3-4 hours a time)?

play for excitement?

get restless and irritable if they can't play?

sacrifice social and sporting activities?

play instead of doing their homework?

try to cut down their playing but can't?

If the answer is "yes" to more than four of these questions, then your child may be playing too much.

So what do you do now?

Give children educational rather than violent games.

Encourage video game playing in groups rather than as a solitary activity.

Set time limits on children's playing time. Tell them they can play for a couple of hours after they have done their homework - not before.

Ensure children follow the video game manufacturer's recommendations. For example, they should sit at least two feet from the screen, play in a well-lit room, never have the screen at maximum brightness, and never play when feeling tired.

Finally, if all else fails, take away the games console and give it back on a part-time basis when appropriate.

One symptom of over-exposure which parents might pick up on is stiffness in their children's movements.

With 40% of family homes now containing computers, there is plenty of opportunity for children to get to a screen.

But most terminals are set up for parents, and the children are the ones who make do.

Looking forward to RSI?

The resulting bad posture is one of the chief causes of repetitive strain injury (RSI) among children, according to Bunny Martin, director of the Body Action Campaign, a charity trying to combat the disorder among young people.

She says children as young as seven are suffering from RSI because of overuse of computers at school and in the home.

In some classes of 11-year-olds, she has found that more than half the pupils have the first signs of the condition.

Cold cure

A 13-year-old-boy from Peckham, south west London, told her: "At night my thumbs are so painful I have to sit with them in cold water to take the pain away."

Ms Martin says many games are set up to encourage children to chase high scores.

"They forget about taking breaks," she said.

Young guns: Are violent games a bad influence?

Both teachers and parents must be vigilant, she added.

"Some children are even having to give up their studies because the pain makes studying impossible.

"Kids will even practise under the duvet at night, if you let them."

A constant criticism levelled against video games has been that the majority feature aggressive elements.

Calm down

This in turn has been used to argue that children become more aggressive as a result of playing them.

The controversy has raged for 15 years, but little systematic research has been carried out, and the debate becomes increasingly relevant as new games use more explicit representations of extreme and realistic violence.

The theory of social learning says that playing aggressive video games leads to the stimulation of aggressive behaviour.

On the other hand, the catharsis theory suggests that playing aggressive video games has a relaxing effect by channelling and releasing aggression.

Dr Griffiths says that while more research is needed, it now seems clear a child's play after watching a violent video game becomes more aggressive.

"It is probably the case that violent video games have a more pronounced effect in young children but less of an effect - if any - once they have reached their teenage years," he added.